Fix handling unknown branches when parsing switch instructions.

Fix handling unknown branches when parsing switch instructions.

The bitcode reader for the switch insruction did not check if the
branch labels were defined. This patch fixes the problem. Includes
test for such a case.

BUG=None
R=stichnot@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=0042fea38a41488f6da0e49fbe810fcb3bb88622

[Karl, 2015-08-20 20:31:05]

kschimpf@google.com changed reviewers:
+ jvoung@chromium.org, stichnot@chromium.org

[Jim Stichnoth, 2015-08-20 21:18:04]

lgtm

https://codereview.chromium.org/1303003002/diff/20001/tests_lit/parse_errs/ba...
File tests_lit/parse_errs/bad-switch-case.test (right):

https://codereview.chromium.org/1303003002/diff/20001/tests_lit/parse_errs/ba...
tests_lit/parse_errs/bad-switch-case.test:1: 
Remove blank lines at beginning and end of file

[Karl, 2015-08-21 16:41:05]

Committed patchset #3 (id:40001) manually as
0042fea38a41488f6da0e49fbe810fcb3bb88622 (presubmit successful).

[Karl, 2015-08-21 16:41:17]

https://codereview.chromium.org/1303003002/diff/20001/tests_lit/parse_errs/ba...
File tests_lit/parse_errs/bad-switch-case.test (right):

https://codereview.chromium.org/1303003002/diff/20001/tests_lit/parse_errs/ba...
tests_lit/parse_errs/bad-switch-case.test:1: 
On 2015/08/20 21:18:03, stichnot wrote:
> Remove blank lines at beginning and end of file

Done.